Pope Francis spoke during the Mass at the Papal Basilica of St. Paul's Outside the Walls in Rome on Sunday, stressing that inconsistency between what pastors and Christians preach and what they practice is undermining the Catholic Church's credibility.

Peter and the Apostles proclaimed the Gospel of Jesus courageously and fearlessly, but "are we capable of bringing the word of God into the environment in which we live?" asked the pope, who inherited a Church plagued with a series of scandals, including sexual abuse of children by priests.

"Let us all remember this: one cannot proclaim the Gospel of Jesus without the tangible witness of one's life," Pope Francis said at St. Paul's, one of Rome's four major basilicas and the second largest after St. Peter's. "Those who listen to us and observe us must be able to see in our actions what they hear from our lips, and so give glory to God!"

The pontiff also referred to Saint Francis of Assisi – whose name he took after he was elected last month – sharing one of the quotes by the 12th century Italian friar: preach the Gospel and, if necessary, use words.

"Preaching with your life, with your witness. Inconsistency on the part of pastors and the faithful between what they say and what they do, between word and manner of life, is undermining the Church's credibility," said the pope, who spoke on proclamation, witness and worship.

Faith is born from listening, and is strengthened by proclamation, he said, adding that proclamation was not a mandate of the clergy alone. "We all have to proclaim and bear witness to the Gospel. We should all ask ourselves: How do I bear witness to Christ through my faith? Do I have the courage of Peter and the other Apostles, to think, to choose and to live as a Christian, obedient to God?"

But this is possible "only if we recognize Jesus Christ, because it is he who has called us, he who has invited us to travel his path, he who has chosen us," the pope said. "Proclamation and witness are only possible if we are close to him, just as Peter, John and the other disciples..."

Pope Francis also spoke about the importance of worship. "Do we turn to God only to ask him for things, to thank him, or do we also turn to him to worship him? What does it mean, then, to worship God?"

Worship, he said, means learning to be with Jesus, "it means that we stop trying to dialogue with him, and it means sensing that his presence is the most true, the most good, the most important thing of all."

"All of us, in our own lives, consciously and perhaps sometimes unconsciously, have a very clear order of priority concerning the things we consider important. Worshipping the Lord means giving him the place that he must have; worshipping the Lord means stating, believing – not only by our words – that he alone truly guides our lives; worshipping the Lord means that we are convinced before him that he is the only God, the God of our lives, the God of our history."

In the end, the pope said he wanted a question to resound in the heart of all. "Have I considered which idol lies hidden in my life that prevents me from worshipping the Lord? Worshipping is stripping ourselves of our idols, even the most hidden ones, and choosing the Lord as the centre, as the highway of our lives."